Lubricating composition



atented July 27, 1943 UNITED STATES LUBRICATING COMPOSITION PAT'ENT.OFFICE No Drawing. Application May 20, 1941, Serial No. 394,362

5 Claims.

This invention relates to lubricating compositions containing sulfurizedesters of polymerized unsaturated acids having conjugated double bonds,and more particularly to lubricating com- .positions containingsulfurized alkyl esters of isomerized and polymerized unsaturated fattyacids having conjugated double bonds.

The compounds of the present invention may be prepared by heatingmonoalkyl esters of unsaturated fatty acids until they become isomerizedand polymerized, substantially as described by one of us in Industrialand Engineering Chemistry 32, 802-808 .(1940) and 33, 86-89 (1941). Theresulting isomerized and polymerized esters having conjugated doublebonds are then heated with sulfur to produce the correspondingsulfurized esters.

We have found that the sulfurized esters of polymerized unsaturatedfatty acids having conjugated double bonds, particularly thosecontaining fro about of sulfur, impart excellent properties tolubricating compositions when incorporated therewith. Sulfurized oilsand sulfurized esters have been used in the past in extreme pressurelubricants and as corrosion inhibitors in lubricating compositionsgenerally, but these substances have never been entirely satisfactorydue, in large measure, to their relative instability. The advantages ofthe improved lubricating properties obtained by the use of thesulfurized esters and oils of the prior art were often off-set by theformation of undesirable byproducts resulting from decomposition of thematerial added to the lubricant. The sulfurized esters of the presentinvention, however, have been found to produce lubricating compositionsof excellent properties with substantially no decomposition of theesters and consequent formation of undesirable by-products.

It is an advantage of the present invention, therefore, that itsproducts are very stable. Little or no sludge formation due to theproduction of resinous products takes place at the high temperaturesprevailing in internal combustion engines, as is the case with theglycerides used in the prior art.

The products of the present invention possess a further advantage inthat they are extremely effective corrosion inhibitors andanti-oxidants. The chief cause of corrosion of metal bearings and thelike is the decomposition of hydrocarbon oils to form corrosive acids.This decomposition is catalyzed by the metal of the engine and thereforemay be substantially reduced or completely eliminated by the presence ofa relatively 7 We do not know whether the film formation involves merelya physical adhesion of polar groups to the metal or whether the film isa thin layer of a reaction product of the ester and the metal; theprotection obtained may be due in part to both factors.

Addition of the new sulfurized esters of polymerized unsaturated fattyacids having conjugated double bonds to lubricating compositions leadsto improved viscosity characteristics and increased oilin'ess propertiesof the lubricant. A lubricating oil must wet the metal bearing in or derto be effective and accordingly, the best lubricants are those havingincorporated therewith a suitable polar compound since certain polargroups appear to have an afiinity for the metal. The esters of thepresent invention fall into this category of polar compounds. However,we have found that the esters produced from a short chain alcohol and along chain acid are more desirable in lubricating compositions thanthose produced from a long chain alcohol and a long chain acid becauseof the closer packing and orientation of the molecules.

Only a small amount of the esters of the present invention is necessaryto impart improved properties to a lubricating composition. We havefound about /270, if added alone, or about 3%,

if added with soap, to be effective.

The invention will be described in greater detail in conjunction withthe following specific example, it being understood that the inventionis not intended to be limited to the details therein set forth.

Example The methyl esters of dehydrated castor oil fatty acids areisomer-Jed and polymerized by heat treatment at 250-300" C. The majorporobtained.

Other unsaturated fatty acids than those of dehydrated castor oil may beused in the formation of the ester starting material. We have found thefatty acids of soya bean, linseed, cottonseed, corn, perilla, tung,oiticica, sunflower seed, samower seed, sardine and menhaden oils to beentirely satisfactory. Similarly, the invention is not limited to methylesters, but other monoalkyi esters as ethyl, propyl, butyl and the likemay be utilized.

We claim: i

1. A lubricating composition having incorporated therein a sulturizedlower alkyl ester of a polymerized unsaturated higher fatty acid havingconjugated double bonds.

-2. A lubricating composition having incorporated therein a suliurizedlower alkyl ester of an isomerized and polymerized unsaturated higherfatty acid having conjugated double bonds.

it lubricating composition having incorporated therein a sulfurizedlower alkyl ester of a dimerized unsaturated higher fatty acid havingconjugated double bonds.

a. A lubricating composition having incorporated therein a small amountof a sulfurized lower alkyl ester of a dimerized unsaturated higherfatty acid having conjugated double bonds, said ester containing fromabout 1%-15% of sulfur.

5. A lubricating composition having incorporated therein a small amountof the sulfurized methyl ester of dimerized conjugated octadecadienoicacid.

ELMER WILLIAM COOK.

THEODORE FRANKLIN BRADLEY.

